A. Ribonucleases. We have identified and characterized a novel human ribonuclease, RNase k6 (Rosenberg and Dyer (1996) Nuc Acids Res 24: 3507-3513) and five novel murine ribonucleases related to those previously described in eosinophils (Batten et al. (1997) in review). We have also characterized the ribonucleases present in human monocytes (Egesten et al. (1997) BBA in press). We have progressed in our study of the gene regulation of the eosinophil ribonucleases, and shown that the intronic enhancer activity characterized for the gene encoding eosinophil-derived neurotoxin (EDN) is mediated by an NFAT-1 consensus binding site (Handen and Rosenberg (1997) J Biol Chem 272: 1665-1669). The NFAT-1 consensus site is also present in the LTR promoter of HIV, which we studied in the context of chemokine suppression of viral transcription (Handen and Rosenberg (1997) FEBS Lett. in press). B. Antiviral activity of eosinophil secretory proteins. We have shown that human eosinophils are active against isolated virions of both a laboratory strain of a murine retrovirus (Domachowske and Rosenberg (1997) J Leukoc Biol. in press) and, more important, against isolates of respiratory syncytial virus (RSV), types A and B (Domachowske and Rosenberg (1997a) in review). Other studies have provided support for a role for eosinophils in the host defense against RSV (Domachowske and Rosenberg (1997b) in review). Finally, we have gone on to show that recombinant human eosinophil-derived neurotoxin, the major eosinophil ribonuclease, can act on its own as an antiviral agent against RSV (Domachowske and Rosenberg (1997c) in review), suggesting the possibility of developing EDN as aerosolized agent for the treatment of this respiratory infection (Rosenberg and Domachowske, provisional US patent NIH E-161-97/0 filed 7/2/97). C. Miscellany. Extending from our main projects, we have shown that the genomic structure of the eosinophil Charcot-Leyden crystal protein gene is analogous to those of the related sugar-binding galectins (Dyer and Rosenberg (1997) Genomics 40: 217-221).